Confirmed here with Yosemite 10.10.5 and Eucon 3.3.2. I fired up Eucon with a Mix and a Transport with no PT session. Initial memory consumption on startup is just over 19MB. After an hour, it was just over 3x that (63MB).

If I start up a PT 12.4 session with moderate fader movement and transport activity after a reboot, and work for half an hour, Eucon memory usage increased to well over 800MB (42x).

The memory leak definitely appears to be worse with usage as opposed to running idle. I think we just uncovered what's causing Eucon to crash after a couple of hours. If you never reboot, I could see this definitely affecting system performance and stability over time.